Electric pump

ABSTRACT

In an electric pump, a vortex chamber may be formed by a clearance between an outer circumferential surface of an impeller and an inner circumferential surface of a casing. A low rigidity part may be provided to a supporting portion or a shaft, or to both of them. The low rigidity part may be formed such that while the electric pump operates, a center point of the shaft in a top view of the shaft moves along a specific line which is parallel to a tangent line of the outer circumferential surface of the impeller at the specific position and passes through the center point of the shaft while the electric pump does not operate, or moves to one of two areas divided by the specific line. The one of the two areas may he opposite to the other of the two areas that includes the specific position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No. 2011-276072, filed on Dec. 16, 2011, the contents of which are hereby incorporated by reference into the present application.

TECHNICAL FIELD

The present application relates to an electric pump.

DESCRIPTION OF RELATED ART

Japanese Patent Application Publication No. H8-261194 discloses a pump including a shaft, an impeller, and a pulley. The impeller is fixed on an end of the shaft. The pulley is fixed on the other end of the shaft. The shaft is rotatably supported by a bearing. The shaft is provided with a low rigidity flexible portion, which has a smaller cross-sectional area than other portion of the shaft, between the pulley and the hearing. In this pump, the pulley is rotated by applying tension to a belt wound around the pulley. When the pulley rotates, the shaft rotates relative to the bearing. Consequently, the impeller rotates.

When tension is applied to the belt, bending moment acts on the shaft. At this time, the flexible portion deflects, thereby reducing the bending moment of the shaft near the bearing.

SUMMARY

When a pump operates, a shaft receives external force such as fluid pressure or vibration. An impeller fixed on a shaft moves according to deformation of the shaft. As a result, the impeller may come into contact with a casing containing the impeller. When the impeller comes into contact with the casing, rotation of the impeller is interrupted by frictional force of the impeller and the casing, and pump efficiency is reduced. On the other hand, in order to prevent contact of the impeller and the casing, when a space between the impeller and the casing is increased, pressure rising of fluid is prevented, and the pump efficiency is reduced. In the present specification, an electric pump that suppresses the reduction in the pump efficiency by suppressing the contact of the impeller and the casing is provided.

An art disclosed in the present application relates to an electric pump. The electric pump may comprise a casing, a shaft, a rotor, an impeller and a stator. The casing may be configured to form a motor chamber and a pump chamber. A lower edge side of the shaft may be configured to be supported by a supporting portion disposed on the casing. The rotor may be configured to rotate around the shaft. The impeller may be configured to be fixed on an upper side of the rotor and be contained rotatably in the pump chamber. The stator may be configured to be disposed on an outer circumferential side of the rotor in the motor chamber. A vortex chamber may be configured to be formed by a clearance between an outer circumferential surface of the impeller and an inner circumferential surface of the casing in the pump chamber. Liquid may flow in the vortex chamber. The clearance may be the narrowest at a specific position in a circumferential direction of the impeller. A low rigidity part may be provided to the supporting portion or the shaft, or to each of the supporting portion and the shaft. The low rigidity part may have lower rigidity than other part of the supporting portion or the shaft to which the low rigidity part is provided. The low rigidity part may be formed such that while the electric pump operates, a center point of the shaft in a top view of the shaft moves along a specific line, or moves to one of two areas divided by the specific line. The specific line may be parallel to a tangent line of the outer circumferential surface of the impeller at the specific position and passes through the center point of the shaft while the electric pump does not operate. The one of the two areas may be opposite to the other of the two areas that includes the specific position.

When the shaft receives external force such as fluid pressure or vibration while the electric pump operates, the shaft deforms while being in a state of being supported by the supporting portion. Since the aforementioned electric pump includes the low rigidity part, the shaft deforms such that the center point of the shaft in the top view thereof moves along the aforementioned specific line or moves to the one of the divided areas opposite to the other of the divided areas including the aforementioned specific position. As a result, the impeller moves according to the deformation of the shaft. That is, the impeller does not move in a direction in which the clearance between the outer circumferential surface of the impeller and the inner circumferential surface of the casing at the aforementioned specific position reduces. As a result, at the specific position, namely, at the position where the clearance between the outer circumferential surface of the impeller and the inner circumferential surface of the casing is the narrowest, the contact of the outer circumferential surface of the impeller and the inner circumferential surface of the casing may be prevented. According to this configuration, it is not necessary to increase the clearance between the outer circumferential surface of the impeller and the inner circumferential surface of the casing at the specific position in consideration of the deformation of the shaft. Therefore, the reduction in the pump efficiency may be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic longitudinal cross-sectional view of an electric pump according to a first embodiment.

FIG. 2 is a schematic view representing a state where a shaft deflects.

FIG. 3 is a view for illustrating a state of movement of a center point of the shaft.

FIG. 4 is a schematic longitudinal cross-sectional view of an electric pump according to a second embodiment.

FIG. 5 shows a cross-sectional shape of a small diameter portion according to the second embodiment.

FIG. 6 is a schematic longitudinal cross-sectional view of an electric pump according to a third embodiment.

FIG. 7 is a schematic longitudinal cross-sectional view of an electric pump according to a fourth embodiment.

FIG. 8 shows a cross-sectional shape of a low rigidity part according to the fourth embodiment.

FIG. 9 shows a cross-sectional shape of a void according to a modification.

FIG. 10 shows a cross-sectional shape of a void according to another modification.

FIG. 11 shows a cross-sectional shape of a small diameter portion according to yet another modification.

DETAILED DESCRIPTION

Representative, non-limiting examples of the present invention will now be described in further detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed below may be utilized separately or in conjunction with other features and teachings to provide improved electric pumps, as well as methods for using and manufacturing the same.

Moreover, combinations of features and steps disclosed in the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the below-described representative examples, as well as the various independent and dependent claims, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.

The electric pump described herein may include one or more of the following features. The low rigidity part may be included in the shaft. The low rigidity part may be formed on the lower edge side of the shaft. The other part of the shaft may he formed on the upper edge side of the shaft. According to this configuration, in a case where the shaft receives external force, the lower edge side of the shaft as the low rigidity part deflects, so that deflection of the other part of the shaft may be suppressed. As a result, deflection of a part passing through the rotor of the shaft may be suppressed. Therefore, the shaft and the rotor are prevented from contacting one another with large force.

A cross-sectional area of the low rigidity part of the shaft in a direction vertical to an axis direction of the shaft may be smaller than that of the other part of the shaft in the direction. Alternatively, the low rigidity part may comprise an elastic member formed of a material having an elastic coefficient smaller than that of the other part of the shaft.

The low rigidity part may be included in the supporting portion, that is, the low rigidity part may be disposed at a part of the supporting portion. According to this configuration, in the case where the shaft receives external force, since the low rigidity part disposed on the supporting portion is deformed, and the deflection of the shaft may be suppressed as compared with a configuration in which the supporting portion firmly supports the shaft.

First Embodiment

An electric pump 10 according to the present embodiment is installed in an engine room of a vehicle, and used in order to circulate cooling water cooling an engine, an inverter, or the like. As shown in FIG. 1, the electric pump 10 com_(p)s a pump portion 20 and a motor portion 40. Outer walls of the electric pump 10 are configured by a casing 12.

The pump portion 20 is formed in an upper casing 14 of the easing 12. The pump portion 20 has a pump chamber 26 formed by the upper casing 14. A suction opening 22 and a discharge opening (not shown) formed by the casing 12 are connected to the pump chamber 26. The suction opening 22 is connected to an upper edge of a pump chamber 26. The discharge opening extends in a tangential direction of an outer circumference of the pump chamber 26. In the pump chamber 26, an impeller 28 of a rotating body 30 is disposed. The impeller 28 has a circular shape in its top view, and has an upper surface inclined upward from outer circumference toward a center in its side view. On the upper surface of the impeller 28, a plurality of blades is formed at regular intervals.

An outer circumferential surface 28 a of the impeller 28 faces an inner circumferential surface 14 a of the upper casing 14. A vortex chamber 24 is formed between the outer circumferential surface 28 a and the inner circumferential surface 14 a. FIG. 3 is a schematic view of a case where the inner circumferential surface 14 a of the upper casing 14 is viewed from above. As shown in FIG. 3, a width of the vortex chamber 24 is the smallest at a position 24 a. In other words, clearance between the outer circumferential surface 28 a and the inner circumferential surface 14 a is the narrowest at the position 24 a. The width of the vortex chamber 24 gradually increases as proceeding in a rotational direction R of the impeller 28. The vortex chamber 24 is connected to the discharge opening at a position where the width of the vortex chamber 24 is the largest.

As shown in FIG. 1, the motor portion 40 is disposed below the pump portion 20. The motor portion 40 is formed in a lower casing 16 of the casing 12. The motor portion 40 has a motor chamber 48 formed by the lower casing 16. The motor portion 40 comprises a shaft 44, a rotor 42, and a stator 46. A lower edge part of the shaft 44 is fixed on a supporting portion 52 of the lower casing 16. The supporting portion 52 makes a circuit of the lower edge part of the shaft 44 in a circumferential direction of the shaft 44 to support the shaft 44. The shaft 44 vertically extends in the casing 12, and a front edge thereof reaches inside the pump chamber 26.

In the shaft 44, a void 44 a extending upward from a lower edge is formed. A cross-section of the void 44 a (i.e., cross-section in a direction vertical to an axis direction of the shaft 44) is circular. A length range 44 b where the void 44 a is formed has lower rigidity than other part of the shaft 44. Hereinafter, the length range 44 b of the shaft 44 is referred to as a low rigidity part 44 b.

As shown in FIG. 3, in the low rigidity part 44 b, when the cross-section in the direction vertical to the axis direction of the shaft 44 is viewed, a center X1 of the cross-section of the void 44 a (shown by a broken line) is located on a line L2. The center X1 is offset rightward from a center point 44 c of the shaft 44. In addition, in a first modification (see FIG. 10), the center X1 may be located in an area S1. The area S1 is an area that does not include the position 24 a among two areas divided by the line L2 that is parallel with a tangent line L1 of the impeller 28 at the position 24 a (i.e., position where the width of the vortex chamber 24 is the smallest) and passes through the center point 44 c of the shaft 44 while the electric pump 10 stops. An area S2 is an area that includes the position 24 a among the two areas divided by the line L2.

The rotating body 30 is rotatably fixed on the shaft 44. The rotating body 30 comprises an impeller 28 and a rotor 42. The cylindrical rotor 42 is provided below the impeller 28, and is disposed in the motor chamber 48. The rotor 42 is fowled by a magnetic material, and is subjected to magnetization treatment so as to have a plurality of magnetic poles in a circumferential direction. The impeller 28 and the rotor 42 are coupled integrally with each other. Therefore, when the rotor 42 rotates, the impeller 28 also rotates. The stator 46 is disposed on an outer circumferential side of the rotor 42, and faces the rotor 42. The stator 45 is connected to an external power supply (not shown) (e.g., a battery installed in a vehicle) through a drive circuit (not shown).

Next, an operation of the electric pump 10 will be now described. When electric power is supplied from the drive circuit to the stator 46, the rotor 42 rotates around the shaft 44. As a result, the impeller 28 rotates, and cooling water is suctioned in the pump chamber 26 from the suction opening 22. The cooling water suctioned in the pump chamber 26 is pressurized by the rotation of the impeller 28 to be discharged outside the casing 12 from the discharge opening.

While the electric pump 10 operates, external force is applied to the shaft 44 due to water pressure of the cooling water, vibration, eccentricity of the rotor 42, or the like. The shaft 44 is in a state of a cantilever where the lower edge is supported by the supporting portion 52. Therefore, when the shaft 44 receives the external force, a part supported by the supporting portion 52 serves as a fixed edge of the cantilever and the shaft 44 deflects.

The shaft 44 has the low rigidity part 44 b. When the cross-section in the direction vertical to the axis direction of the shaft 44 is viewed, the center X1 of the void 44 a of the low rigidity part 44 b is formed at the position to be offset from the center point 44 c on the line L2 (see FIG. 3). Therefore, the shaft 44 deflects such that the center point 44 c thereof moves onto the line L2 (in the area S1 in the first modification). As a result, the impeller 28 moves with the movement of the center point 44 c. The impeller 28 moves in a direction not coming closer to the inner circumferential surface 14 a of the upper casing 14 at the position 24 a (i.e., direction parallel with the tangent line L1 (direction to part away from the position 24 a in the first modification)). According to this configuration, it is not necessary to increase the width of the vortex chamber 24 at the position 24 a in consideration of the deflection of the shaft 44. The smallest width of the vortex chamber 24 can be kept small, and hence, pump efficiency can be improved as compared with a case where the width of the vortex chamber 24 is set large.

As shown in FIG. 2, when the shaft 44 deflects, the shaft 44 comes into contact with the rotating body 30 at contact positions CP1, CP2. The low rigidity part 44 b is formed on the lower edge part of the shaft 44, and hence the shaft 44 significantly deflects on the low rigidity part 44 b near the supporting portion 52. As a result, bending moment of the shaft 44 located within a though hole 30 a of the rotating body 30 is reduced. According to this configuration, an amount of deflection of the shaft 44 located in the through hole 30 a can be suppressed.

Assuming that the amount of deflection of the shaft 44 located in the through hole 30 a is increased, the shaft 44 and the rotating body 30 come into contact with each other also on a side opposite to the contact positions CP1, CP2 with the shaft 44 therebetween. As a result, sliding resistance of the shaft 44 and the rotating body 30 is increased, resulting in a possibility that a situation where rotation of the rotating body 30 is interrupted occurs. in the electric pump 10, occurrence of such a situation can be suppressed.

Second Embodiment

Description of difference from the first embodiment will be made. As shown in FIG. 4, in an electric pump 100 according to a second embodiment, a shape of a shaft 144 is different from that of the shaft 44. While the shaft 144 is not formed with void 44 a, the shaft 144 is formed with a small diameter portion 144 a. The small diameter portion 144 a is disposed on a lower edge side of a through hole 30 a above a supporting portion 52. The small diameter portion 144 a is a column having a diameter smaller than that of other portion of the shaft 144.

As shown in FIG. 5, a center X2 of the small diameter portion 144 a is located in an area S2 (i.e., area on a position 24 a side). The center X2 is offset so as to come close leftward with respect to a center point 144 c of the shaft 144 (i.e., a side where a width of a vortex chamber 24 is narrow). In addition, in a second modification, the center X2 may be on a line L2. However, the center X2 and the center point 144 c may not coincide with each other. A part where the small diameter portion 144 a is located has lower rigidity than other portion of the shaft 144 (hereinafter, referred to as a “low rigidity part 144 b”).

When external force is applied to the shaft 144 while the electric pump 100 operates, the shaft 144 significantly deflects at the low rigidity part 144 b. The center X2 of the small diameter portion 144 a is located on the area S2 side (i.e., on the line L2 in the second modification), and hence the center point 144 c of the shaft 144 deflects so as to move onto the line L2 or into an area S1 when the shaft 144 is viewed from above. Thus, the electric pump 100 can produce an effect similar to the electric pump 10.

Third Embodiment

Description of difference from the second embodiment will be made. As shown in FIG. 6, in an electric pump 200 according to a third embodiment, a shape of a shaft 244 is different from that of the shaft 144. The shaft 244 is formed with a small diameter portion 244 a similar to the small diameter portion 144 a. An elastic member 244 b is disposed around the small diameter portion 244 a. The elastic member 244 b is formed by a material having a smaller elastic coefficient than the shaft 244, such as elastically deformable rubber or aluminum. A part configured by the small diameter portion 244 a and the elastic member 244 h has lower rigidity than other part of the shaft 244 (hereinafter, referred to as a “low rigidity part 244 c”). The electric pump 200 can produces an effect similar to the electric pump 100.

Fourth Embodiment

Description of difference from the first embodiment will be made. As shown in FIG. 7, in an electric pump 300 according to a fourth embodiment, a shaft 344 and a supporting portion 352 are different from the shaft 44 and the supporting portion 52, respectively. A lower edge part of the shaft 344 is not formed with a void. That is, the shaft 344 has a solid columnar shape. In addition, in a modification, the shaft 344 may be similar to the shaft 44, 144 or 244.

The supporting portion 352 is formed with a low rigidity part 352 a, when a cross-section in a direction vertical to an axis direction of the shaft 344 is viewed. As shown in FIG. 8, the low rigidity part 352 a is formed in an area S1. In FIG. 8, only the low rigidity part 352 a in the supporting portion 352 is extracted to be shown. The low rigidity part 352 a is in contact with an outer circumferential surface of the shaft 344. The low rigidity part 352 a is formed by a material having a smaller elastic coefficient than other part of the supporting portion 352, such as elastically deformable rubber. The electric pomp 300 can produces an effect similar to the electric pump 100.

Modifications

(1) The void 44 a of the shaft 44 according to the first embodiment may be filled with a material having a smaller elastic coefficient than the shaft 44.

(2) According to each of the aforementioned embodiments, only one of the shaft 44 or the like and the supporting portion 52 or the like is formed with the low rigidity part 44 b or the like. However, both of the shaft 44 or the like and the supporting portion 52 or the like may be provided with low rigidity parts, as an electric pump including the shaft 44 and the supporting portion 352, for example.

(3) According to the aforementioned second and third embodiments, the small diameter portions 144 a, 244 a are prepared by the same materials as other portions of the shafts 144, 244. However, the small diameter portions 144 a, 244 a may be prepared by materials having smaller elastic coefficients than other parts of the shaft 144, 244.

(4) According to the aforementioned first embodiment, on the low rigidity part 44 b, when the cross-section in the direction vertical to the axis direction of the shaft 44 is viewed, the center of the cross-section of the void 44 a is in the area S1 shown in FIG. 3. However, the void 44 a may be formed such that on the low rigidity part 44 b, rigidity of a put located on the area S1 is smaller than that of a part located on the area S2. Similarly in the configurations according to the second and third embodiments, on each of the low rigidity parts 144 b. 244 c, rigidity of a part located on the area S1 may be smaller than that of a part located on the area S2.

(5) According to the aforementioned first embodiment, the cross-section of the void 44 a is circular. However, the cross-section of the void 44 a is not limited to a circular shape. The cross-section of the void 44 a may be polygonal such as a square shape. Alternatively, as shown in FIG. 9, the cross-section of the void 44 a may be oval.

(6) According to the aforementioned first embodiment, the center X1 of the void 44 a is located on the line L2. However, as shown in FIG. 10, the center X1 may be located in the area S1 abovementioned as the first modification.

(7) The small diameter portion 144 a according to the aforementioned second embodiment may not be columnar. For example, as shown in FIG. 11, the small diameter Portion 144 a may have such a shape that a notch is formed on a part of the area S1 as compared with other part of the shaft 144. Generally speaking, the small diameter portion 144 a may have a shorter outer circumferential length than the other part of the shaft 144. Further, the small diameter portion 144 a may be formed in the area S2, when a cross-section in a direction vertical to an axis direction of the shaft 144 is viewed. The small diameter portion 244 a is also similar.

(8) Furthermore, when the cross-section in the direction vertical to the axis direction of the shaft 344 is viewed, a part of the low rigidity part 352 a may be formed in an area 52 in FIG. 8. The low rigidity part 352 a may be formed such that a center point of the shaft 344 in viewing the shaft 344 from above moves along a line L2 or moves to the area S1, when pressing force acts on the supporting portion 352 from the shaft 344 by external force applied to the shaft 344, and the low rigidity part 352 a is elastically deformed. 

1. An electric pump comprising: a casing configured to form a motor chamber and a pump chamber; a shaft of which lower edge side is configured to be supported by a supporting portion disposed on the casing; a rotor configured to rotate around the shaft; an impeller configured to be fixed on an upper side of the rotor and be contained rotatably in the pump chamber; a stator configured to be disposed on an outer circumferential side of the rotor in the motor chamber; and a vortex chamber configured to be formed by a clearance between an outer circumferential surface of the impeller and an inner circumferential surface of the casing in the pump chamber, wherein liquid flows in the vortex chamber, the clearance is the narrowest at a specific position in a circumferential direction of the impeller, a low rigidity part is provided to the supporting portion or the shaft, or to each of the supporting portion and the shaft, the low rigidity part having lower rigidity than other part of the supporting portion or the shaft to which the low rigidity part is provided, and the low rigidity part is formed such that while the electric pump operates, a center point of the shaft in a top view of the shaft moves along a specific line, or moves to one of two areas divided by the specific line, the specific line being parallel to a tangent line of the outer circumferential surface of the impeller at the specific position and passing through the center point of the shaft while the electric pomp does not operate, and the one of the two areas being opposite to the other of the two areas that includes the specific position.
 2. The electric pump as in claim 1, wherein the low rigidity part is included in the shaft, the low rigidity part is formed on the lower edge side of the shaft, and the other part of the shaft is formed on the upper edge side of the shaft.
 3. The electric pump as in claim 2, wherein a cross-sectional area of the low rigidity part of the shaft in a direction vertical to an axis direction of the shaft is smaller than that of the other part of the shaft in the direction.
 4. The electric pump as in claim 2, wherein the low rigidity part comprises an elastic member formed of a material having an elastic coefficient smaller than that of the other part of the shaft.
 5. The electric pump as in claim 1 wherein the low rigidity part is included in the supporting portion, and the low rigidity part is disposed at a part of the supporting portion. 